Lee's tip-off note (7)
I believe the answer is:
epistle
'note' is the definition.
(thesaurus)
'lee's tip-off' is the wordplay.
'off' indicates anagramming the letters.
'lees'+'tip'='leestip'
'leestip' is an anagram of 'EPISTLE'.
(Other definitions for epistle that I've seen before include "Pets lie (anag)" , "may read this" , "Missive; letter" , "Letter from a saint" , "Writing" .)